In view of the improvement of connection workability of an optical connector ferrule, it has been recently provided a so-called MPO connector (optical connector having a structure in which a multi-core connector ferrule, which is stipulated in the JIS-C5982 standard etc., is received within a plastic housing).
Conventionally, as shown in FIGS. 17A and 17B to be described later, the MPO type plug body 1 receives at the end (front end) of a sleeve-like housing 18 a ferrule 12 which is fitted to a head of a multi-core optical fiber cord FT. Within the housing 18, there is provided a spring 15 which elastically urges the ferrule 12 toward the front side of the plug body 1.
Further, the MPO type plug body 1 includes a housing 18 with a spring receiving recess 17, a cylindrical coupling 13 which is externally fitted in a slidable manner within a movable range reserved in an axial direction thereof with respect to the housing 18, and is elastically urged toward the front side of the plug body 1 by the action of a spring 16 received in the recess 17 of the housing 18. a spring bush 11 which is attached to the rear end opposed to the front end at which the ferrule 12 of the housing 18 is provided, and a boot 19 which is externally inserted into the rear end of the spring bush 11.
It is configured such that fitting of the plug body 1 to an adaptor 21 is carried out by inserting a portion positioned in a rearward direction of the coupling 13 in the plug body 1, e.g. the boot 19 toward the adaptor 12 with a finger of an operator.
Meanwhile, it is configured such that extraction of the plug body 1 from the adaptor 21 is carried out by pulling in the coupling 13 to the boot 19 side against an elastic urging force of the spring 16.
For example, as shown in FIG. 17B, when the end side of the housing 18 of the plug body 1 is first forcibly inserted into the adaptor 21, the end of the coupling 13 is pushed by an elastic engaging part 22 of the adaptor 21, and the coupling 13 is once retreated. At this time, a space 22b into which the end of the coupling 13 is entered becomes empty within the adaptor 21 and gest into a free state where the elastic engaging part 22 is free to vertically move. Therefore, inserting the plug body 1 into the adaptor 21 upwardly moves an engaging projection 22a of the elastic engaging part 22 within the space 22b and gets into a state where the plug body 1 can be engaged with the adaptor 21.
However, when the plug body 1 is forcibly pulled out in this state, the engaging projection 22a of the elastic engaging part 22 upwardly moves within the space 22b at this rate, resulting in that the adaptor 21 easily comes off. Then, the space 22b is closed by advancing the coupling 13 to block up the space 22b. 
Thus, the coupling 13 is engaged with a spring stopper 13b as is already mentioned, and is urged t all the time toward the font side of the housing 18 by the action of the spring 16 received in the recess 17. Therefore, the coupling 13 is kept in condition of being held at an advance position. This shields and holds the space 22b of the elastic engaging part 22 of the adaptor 21 by the end of the coupling 13, and prevents upward movement of the engaging projection 22a. Therefore, an engaging convex portion 31 of the plug body 1 is engaged with the elastic engaging part 22 of the adaptor 21, thereby preventing the plug body 1 is being pulled out therefrom.
When the plug body 1 is removed, the coupling 13 is forcibly retreated from a state where the coupling 13 is held at an advancing position by hooking a finger on the coupling 13 to put a space 22b within the adapter 21 for receiving the end of the coupling 13 into a free state.
Namely, when the coupling 13 is slid backwardly, a hooking part 31a in a state where the engaging projection 22a of the elastic engaging part 22 of the adaptor 21 is engaged and the engaging convex part 31 are exposed. When the plug body 1 is forcibly pulled out therefrom in this state, the engaging projection part 22a of the elastic engaging part 22 which bits into the hooking part 31a, and is engaged with the engaging convex part 31 gets over the engaging convex part 31 and is released while expanding by virtue of the space 22b. 
After the plug body 1 is pulled out from the adaptor 21, a finger is taken off from the coupling 13, thereby elastically advancing and returning the coupling 13 to an initial position by the action of the spring 16.
Recently, as shown in FIG. 16, under the circumstances where the densification of a communication system in the various data centers has become essential, insertion of the plug body 1 into the adaptor 21 by inserting a finger one by one or a pulling operation (disengaging operation) takes troublesome labor and great amounts of time, and therefore makes workability thereof very worse.
Conventionally, a disengaging operation of the plug body 1 has been heretofore prevailing using a tab in order to improve the efficiency of a pulling-in operation or a pulling-out operation (disengaging operation) of a number of plug bodies 1.
In other words, as a tab of this kind, the tab is provided at its end with a U-shaped cover-like tab body and at its rear end with gripping member. The tab body is fitted at the outer side of the coupling 13 of the plug body 1 and the tab body is moved back and forward by operating the grasping member. Thereby, the plug body 1 is subjected to a disengaging operation together with the coupling 13 from the adaptor 21.
Specifically, as shown in PATENT LITERATURE 1 and PATENT LITERATURE 2, the optical connector adaptor is publicly known in which the tab body is formed into a substantially U-shape and the coupling 13 is internally fitted from an insertion opening.
Moreover, as shown in PATENT LITERATURE 3, the optical connector tab is publicly known in which a tab body is made of spring member having a thin sheet chevron shape whose tab body is bifurcated, and left and right outer wall surfaces of the coupling 13 are clamped by the spring member.